Exception: the airport will take it from you, or you will not board the plane with one.
Discussion
Yeah, so damn stupid. Prior to the TSA bs max length you could bring on a plane was 4"...i remember going through security in Atlanta with a Cold Steel Voyager that was 3 7/8" and they were in an uproar... They had to measure it and check the regs (I knew the regs) that would have been late 1990's.
Now I'll either check a bag for all my edc shit or if I can't I'll pick up a throw away at Lowes or Walmart. Those $10 Ozark Trail ones.